Efficient Storage Techniques for Digital Continuous Multimedia

Advances in storage and networking have led to the development of multimedia computing systems capable of offering services such as multimedia mail, news distribution, advertisement, and entertainment. Supporting such services requires the integration of storage and transmission of multimedia data with computing. In this paper, we address the problem of collocational storage of media strands, which are sequences of continuously recorded audio samples or video frames, on disk. We present a model that relates disk and device characteristics to the playback rates of media strands, and derives storage patterns so as to guarantee continuous retrieval of media strands. To efficiently utilize the disk space, we develop mechanisms for merging storage patterns of multiple media strands, by filling the gaps between media blocks of one strand with media blocks of other strands. We propose both an on-line algorithm suitable for merging a new media strand into a set of already stored strands, and an off-line merging algorithm that can be applied a priori to the storage of a set of media strands before any of them have been stored on disk. As a consequence of merging, storage patterns of media strands may become perturbed slightly, to compensate which, read-ahead and buffering are required so that continuity of retrieval remains satisfied. We present techniques for minimizing both read-ahead and buffering. These techniques are being implemented in the multimedia storage server being developed at the UCSD Multimedia Laboratory.